HIV is spreading more rapidly in Eastern Europe than anywhere else in the world. Bulgaria and Hungary are still in the early stages of the crisis. However, without efforts to prevent the spread of HIV and AIDS, both countries are likely to fall victim to the HIV/AIDS growth curve that has already affected the rest of Eastern Europe. Bulgarian and Hungarian young men who have sex with men (YMSM) and Roma men and women are at the greatest risk for HIV infection. In both countries, HIV is spread primarily through sexual transmission. Prevention efforts that are undertaken now could help these countries avoid an explosive HIV/AIDS epidemic. YMSM and Roma men in Bulgaria and Hungary are more likely to trust HIV/AIDS information received from someone they know than from an official statement. Therefore, entire social networks will be recruited for this study and the leader of each network will be responsible for delivering the prevention information to his or her peers. This study will evaluate the effectiveness of peer-led HIV/STD risk reduction educational counseling in reducing HIV risk behavior among the social networks of YMSM and Roma men and women in Bulgaria and Hungary.